Samos in Baltimore?
From what I've heard and read this is supposed to be one of the best Greek places in Baltimore. I'm thinking of checking it out as I plan on visiting Baltimore this weekend (from NYC).
It's the best *cheap* Greek place in Baltimore, definitely. Comfort-food heaven: I love the moussaka, dolmathes, and taramasolata. The garlicky chicken and lamb are good, too, if you're counting your calories. Fair warning: This is definitely a neighborhood place they also serve subs and pizza but don't let that scare you off.
For a bit more money and a "better" atmosphere (dim lighting, tablecloths, art on the wall, and all that), try Ikaros, also in Greektown. While you're in Greektown, be sure to visit one of the markets, too. Lots of great Greek cheeses, olives, wines, etc.
If you're thinking of the trendy, fancy, much, much more expensive Greek food that's emerged in Baltimore and Queens, try Black Olive or Karabela's in Fells Point. Both are great; BO is cozy and homey, K's is more for the flashy, trendy crowd.
Samos is great, especially for the money. By the way, it's BYOB. If you happen to forget, there's a small deli across the street that sells Greek (and other) wine).
Opa was one of (if not) the first of the "upscale" Greek restaurants in Baltimore. My wife and I tried it about four years ago and really liked it; we went back a couple of months ago. I'd still recommend it. The service and appetizers are great; our fish was a little too well done though. Nice ambiance as well.